


the longest distance between two places

by JenTheSweetie



Series: a strict progression of cause to effect [2]
Category: Sherlock (TV)
Genre: Exasperated John Watson, M/M, Time Travel, post-s4
Language: English
Status: Completed
Published: 2017-11-01
Updated: 2017-11-04
Packaged: 2019-01-27 18:29:12
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,119
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12587980
Author URL: https://archiveofourown.org/users/JenTheSweetie/pseuds/JenTheSweetie
Summary: The first time Sherlock came home and said, “I just time traveled,” John said, “Mm, okay.  Want a toastie?”





	1. Chapter 1

**Author's Note:**

  * Translation into Русский available: [Наибольшее расстояние между двумя точками](https://archiveofourown.org/works/14027979) by [never_v_hudo](https://archiveofourown.org/users/never_v_hudo/pseuds/never_v_hudo)
  * Translation into Русский available: [Наибольшее расстояние между двумя точками](https://archiveofourown.org/works/14027979) by [never_v_hudo](https://archiveofourown.org/users/never_v_hudo/pseuds/never_v_hudo)



> In the same universe and after (for some value of "after") "a strict progression of cause to effect." Title from The Glass Menagerie.

“Jesus Christ _,_ ” John said as Sherlock materialized in front of him at 2 o'clock on a rainy Tuesday, “how many times do I have to tell you not to do that in the living room?”

“Sorry,” Sherlock said.  “I was aiming for the stairs.”

“Well, you missed,” John said.  “By a lot.”

“Better than the time I ended up on the roof,” Sherlock said.

“I’m sorry,” John said, “the _roof_?”

“Ah,” Sherlock said, “perhaps next week.”

“It’s _startling_ , you realize.  One of these days I’m going to think you’re an intruder and I’m going to shoot you.”

“Here’s a thought,” Sherlock said, “if someone comes in through the window or breaks down the door, it’s probably an intruder, but if they _appear in front of you without warning_ , it’s probably just me.”

“Thanks,” John said.  “I’ll try to keep that in mind.”

-

The first time Sherlock came home and said, “I just time traveled,” John said, “Mm, okay.  Want a toastie?”

“I’m _serious_ ,” Sherlock said.

“Right,” John said. “Did you get chloroformed today or something?”

“Unbelievable!” Sherlock said, stomping into his room.

The _second_  time Sherlock came home and said, “I just time traveled,” he did so seconds after appearing from thin air in the middle of the kitchen, and John said, “Fuck!” and “What the fuck!” and “How the fuck!” and “Fuck!” again, several times, for good measure.

John followed Sherlock to the lab underneath the British Library (“An _underground lab_ , honestly,” John muttered) where they met Mycroft (“I should have figured you’d be involved in something like this, you bloody great supervillain,”) and were introduced to Dr. Johnson, a transfer from Baskerville (“Big surprise there,”) and shown The Machine, as Sherlock called it, upper case letters heavily implied.

“So you’re telling me,” John said, “that you’re allowing _one_  person to test out time travel, and it’s _him_?”

“Well,” Dr. Johnson said, “there are some risks involved, and Mr. Holmes assured us that he would - ”

“I told Mycroft I’d tell Mummy he was disrupting the fabric of reality if he didn’t let me try it first,” Sherlock interrupted.

Mycroft narrowed his eyes.  “Sherlock’s powers of observation and comfort with disguise and deception make him uniquely suited for the task, and of course, we can guarantee his discretion.”

“But is it _dangerous_?” John said.

“Probably not,” Dr. Johnson said.  “We tested it with a wide range of flora and fauna before we moved on to Mr. Holmes.”

“Wonderful,” John said.  “That’s very reassuring.”

-

“You probably have a few questions,” Sherlock said as they emerged back into the sunlight of Euston Road.

“Um, yes, a few,” John said.  “How many times have you done it?”

“Three,” Sherlock said, “including today.”

“And is that today for me, or today for you, or - ”

“It’s today for both of us,” Sherlock said.  “I came from 7 am.”

“And you can go backwards and forwards in time?” 

“Naturally.”

“Have you run into yourself?”

“No,” Sherlock said.  “I take fairly serious precautions not to.  We’re not entirely sure what will happen if I do.”

“Mm,” John said, because the physics was a bit beyond what he’d learnt in lower sixth form.  “So what do you do when you jump?  Hang on, you’re not visiting the future to solve cases or anything, are you?”

“God, no,” Sherlock said, “that would be cheating.”

“What about lottery numbers?  Royal baby names?” John said.

Sherlock looked horrified. 

“I was _joking_ ,” John said.

-

John would have been a bit more annoyed that his flatmate was bending the space-time continuum if it hadn’t been so bloody _convenient_.

“Shit,” John said, looking at his watch as Sherlock rifled through the desk drawer of the man who’d been found decapitated in Hyde Park, “I’m going to be late picking up Rosie.”

“But we’re close, I can _taste_  it,” Sherlock said.

“Well, you’ll have to taste it on your own, because school lets out in fifteen minutes,” John said.

“I’ll deal with it later,” Sherlock said.

“Pardon me?”

“I mean,” Sherlock said, raising his eyebrows significantly, “ _I’ll_  deal with it _later_.”

“Oh,” John said.  “You’ll go back in time and - ”

“Obviously.”

“Right,” John said.  “Brilliant.”

“Daddy,” Rosie said three hours later, when John and Sherlock returned home to find Rosie and Mrs. Hudson tucking into a baked ziti, “Sherlock told me he can _time travel_!” 

“You _told_  her?” John said, whirling on the Sherlock in question.

“ _I_  didn’t,” Sherlock said.  “Well.   _Yet_.  I suppose I will.  Which makes it not my fault.  Since now that I’ve been _told_  I say it, that means I _have_  to - ”

“Yes, I understand the linear nature of time, ta very much,” John said.

“I’ll just go pick her up now,” Sherlock said.

“Why don’t you do that,” John said.

\- 

“Bad news,” Lestrade said.  “The suspect’s gone.”

“Damn,” Sherlock said.  “We must have just missed her, there’s no way she could have gotten away more than five minutes ago, she was _just_  here - ”

He cut himself off.  

“Sherlock,” John said, “what are - ”

“Excuse me,” Sherlock said quickly to Lestrade, “I’m just going to - ”

And then he took off running.

“What the _hell_?” Lestrade said, blinking after him.

“Oh, you know him,” John said vaguely.

“Do I?” Lestrade said.  “Well, anyway, I suppose we’ll put out a bulletin, talk to some of her coworkers and see if she - ”

And that’s when Sherlock frog-marched the suspect out from around the corner.

“Oh,” John said, “looks like he got her!”

“How in the _fuck_ ,” Lestrade muttered, but luckily Sherlock had seemed damn-near magical even _before_  he could time travel, so.

-

“Sherlock, do you know where my keys are?” John said.

“Oh,” Sherlock said from the sofa, “yes, I borrowed them, I got a note about that.”

“You got a _note_  about - damn it, you’ve got to stop taking mine when you jump without yours,” John said.

“I haven’t done it yet!” Sherlock said.  “It’s a future me!”

“Liar,” John said.

“Probably, yes,” Sherlock said.

-

“So here’s a question,” John said, “is it the kind of time travel where if you go back in time, you change things, but nobody else ever knows because the whole world rewrites itself around whatever you changed?”

“You watch too many movies,” Sherlock said, as if this was an unforgivable sin.  “There’s _one_  reality, John, one timeline, exactly one objective series of events.  Time proceeds from the past to the future without stopping and I just happen to pop in at different points.”

“But,” John said, “surely if you _really_  wanted to...”

Sherlock stood up and began to pace.  “Yesterday Marcus Benton killed his employer and then stepped in front of a bus on High Holburn; no matter what, I cannot go back and change that, because it’s already happened,” Sherlock said.  “I could go back and _watch_  it happen, I could shout at him, I could be the one who called 999, for all we know, but nothing I do - _nothing_  - can change it.  Because if I’d changed it, I would have done it by where we currently are in objective time.  It’s not that you _wouldn’t know_  about the other version of events, it’s that it never would have happened in the first place.  Everything happens exactly the way it happens; the fact that there’s a version of me in it from a different place in the timeline doesn’t mean it _changes_.  It just means there’s a part of it that might have to do with me that I haven’t done yet, but will do, will have _always_  done.”

“Huh,” John said.  “But - have you tried?”

Sherlock stared at him for a long time.  “Yes,” he said finally.

“Ah,” John said.  “And?”

“Something always… got in the way,” Sherlock said, a bit vaguely.

“Oh,” John said.

“You’re disappointed,” Sherlock interpreted.  “You wish I could change the past.”

“Obviously,” John said.  “But that power… we’d try to use it for good, and it would get out of control.  I’m glad I don’t have it.  And I’m especially glad _you_  don’t have it.  It would make you even more of an obnoxious all-knowing prick than you already are.”

“Hm,” Sherlock said, settling back in on the sofa.  “Probably shouldn’t tell you I already know who wins the Premier League, then.”

“ _Damn_  you,” John said.

-

“No,” Sherlock said.

“Sherlock,” Mycroft said, “I’ve given you access to a top secret initiative that most of the world doesn’t know exists.  The very _least_  you can do is use that enormous privilege for the greater good.”

“By your very own rules, I am not to utilize this extremely expensive and dangerous technology for frivolous experiments,” Sherlock said.  “I don’t see how this is any different just because it has to do with your cat!”

“Your _what_?” John said, feeling enormously lost.

“I’m not asking you to _intervene_ ,” Mycroft said.  “I’m asking you to return and _observe_.”

“And rescue it before it runs into traffic like it almost certainly did,” Sherlock said disdainfully.

“Jasper has _not_  run into traffic,” Mycroft said.  “He’s _lost_.”

“You have a _cat_?” John said.

“Yes obviously he has a _cat_ , John, honestly,” Sherlock said.  “Haven’t you ever noticed his sleeves?  I won’t do it, Mycroft.  I don’t jump for personal errands.”

“Last week you jumped because John had forgotten to buy milk,” Mycroft said.

“That’s different,” Sherlock said.

John was trying and failing not to laugh.  “Poor Jasper.  First he has the misfortune of living with Mycroft, then he gets hit by a car.  Come on, Sherlock, go look for his cat.”

“Oh, shut up,” Sherlock snapped.  

“Look at you two,” Mycroft said, “already having lovers’ spats.”

“I’m sorry, what?” John said.

“Go away, Mycroft,” Sherlock said.

Mycroft arched an eyebrow.  “I can revoke your travel privileges at any time.”

“ _Fine_ ,” Sherlock said, so dramatically that you’d think he’d just agreed to go back in time to assassinate the queen.  “I’ll look for your bloody cat.”

“Thank you,” Mycroft said.  

“Hang on,” John said, “before you go, can I get a photo?  Your mum would _love_  this moment.”

-

“Are you keeping things from me?” John said.  

Sherlock glanced at him, then back at the play structure where Rosie was currently hanging from her knees, her braid swinging just above the rubbery surface of the ground.  “What do you mean.”

“You know,” John said.  He glanced around; none of the other parents were within hearing distance.  “Stuff from the future.    Like… I don’t know, Rosie losing her first tooth.”

“I haven’t independently confirmed it, but I can assure you that your daughter doesn’t reach adulthood with a mouth full of milk teeth,” Sherlock said.

“You know what I mean,” John said.  “Important stuff.   _Interesting_  stuff.”

“I don’t know what you would consider _interesting_ ,” Sherlock said.  “The results of the American presidential election?  The identity of Molly’s next disastrous boyfriend?  Who gets voted off tonight’s Big Brother?”

“I mean if anyone _dies_  or anything,” John burst out.  “I mean - I don’t know.  Sorry.  If you don’t want to tell me, I - ”

“No, it’s not that,” Sherlock said.  

He paused, and John held his breath.

“I don’t go terribly far into the future,” he said finally.  “It doesn’t feel… right.  To know too much about things that haven’t happened yet.  A few days or a few weeks are fine - I know more than practically everyone else on the planet already anyway, so it doesn’t make too much of a difference, but at a certain point, it’s… lonely.”

Sherlock shifted in his seat slightly.  John regretted asking.

“Right,” John said.  “I don’t really want to know, anyway.”

“But no,” Sherlock said, quietly, “not as far as I’ve seen.”  

“Right,” John said.

They watched Rosie crawl through a tunnel and then careen, laughing, down a slide.  

“You do keep going grey, though,” Sherlock said.

“Fuck off,” John said.

-

One day, John arrived home to a somewhat older Sherlock than he was generally used to rummaging through the bookshelf.

“Oh,” John said, “hello.”

“Do you know where I put my 1934 edition of the Kinetic Theory of Gases?” Sherlock said.

“Er, no,” John said.  “Not off the top of my head.  I’m sorry, did you come back from, uh - ”

“2032,” Sherlock supplied.

“2032,” John said faintly, “to get a hundred year old textbook?”

“It’s not the textbook, it’s what’s _inside_  it,” Sherlock said.  He was going salt-and-pepper at the temples.  “I left myself a note in one of the margins about a case from 2008 involving a distended balloon, and the book in question was unfortunately damaged in a fire a few years ago.”

“A fire,” John said.  “In the flat?”

“Very minor,” Sherlock dismissed.  “It wasn’t even the fire, actually, it was the bloody _sprinklers -_ anyway, I figured I’d come back to before we moved the furniture around.”

“We _move the_  - no,” John said, “actually, no.  Don’t tell me anything.”

“I wasn’t planning to,” Sherlock said.  The beginnings of wrinkles were showing up around his eyes; it made John’s chest feel a little bit tight.

“Except,” John said.  “Um.” 

“You know my methods,” Sherlock said.  “I’m really not going to tell you anything.”

“I think he’s hiding something,” John blurted out.

Sherlock glanced at him.  “Who?”

“You,” John said.  “The one from now.”

“Ah,” Sherlock said.  He turned back to the bookshelf.

“It’s just,” John said, “ever since all of this started, he’s been a bit - odd.”

“Mm,” Sherlock said.  “Well, he’s currently the only known person ever to travel through time, so.  You know.  Got a bit on his mind.”

“Right,” John said.

“But,” Sherlock said, his fingers slowing as he ran them down another stack of books, “you know what might be interesting?”

“What?” John said.

“If you asked him,” Sherlock said, “about the first time he jumped.  Has he told you the story?”

“Oh,” John said.  “Uh, no, I don’t think so.”

“I recommend it,” Sherlock said, a smile playing at his lips.  “There!”  He slid a book from the shelf and flipped through it quickly.  “ _Yes_.  I knew it wasn’t actually a bladder!  Oh, Mycroft is going to look like such an idiot.  I can’t _wait._ ”

“Glad to know the two of you don’t reach any sort of mature brotherly understanding or anything,” John said dryly.

“If anything, Mycroft just became even _more_  insufferable after - actually, no,” Sherlock said, “best not.”  

He turned to John, and John felt suddenly as if Sherlock was x-raying him with his eyes even more than usual, and he - was Sherlock _licking his lips_?  

“You’ll be off, then?” John said, his mouth feeling inexplicably dry.

“I think so,” Sherlock said, glancing at his watch.  “Until I see you.”

And then, with a wink and a tap at his watch, he disappeared.

“Well,” John said, “shit.”

-

“So I had a visitor today,” John said that night after Rosie had gone to bed.  “It was you.”

“Oh?” Sherlock said, not looking up from his phone.

“A future you.  From _quite_  a ways in the future, in fact.”

Sherlock looked up sharply.  “What did he want?” 

“Oh, nothing,” John lied.  “He said something… interesting, though.  A few interesting things, actually.”

“Ah,” Sherlock said.  He set his phone down carefully.  “I imagine you have questions.”

John paused.  “Um,” he said, “yes?”

“I wasn’t intending it hide it from you,” Sherlock said, his cheeks going inexplicably pink.  “I thought it might come up naturally.”

“It?” John said.

“Us,” Sherlock said.

“Us,” John echoed flatly.

Sherlock’s eyes widened, very slightly.  “Oh.  He didn’t say anything about - ”

“No,” John said.  His mouth was dry again.  “He said to ask you about your first jump.  He said I might find it interesting.  So.  What happened on your first jump?”

“Well,” Sherlock said, “there was - it was very - nothing, really.”

“ _Sherlock_.”

“There were - some indications,” Sherlock said, looking at every single thing in the room that wasn’t John.  

“Indications?”

“That our relationship was not - _exactly_  - the way it is today.”

“Our _relationship_ ,” John said.

“Yes,” Sherlock said.

“Um,” John said.

They stared at each other.

“Causality,” Sherlock said, “can be very perplexing.”

-

After that, John had said a few things that he couldn’t really remember later, and then Sherlock had said, “Wasn’t it obvious?” and John had said, “But it didn’t seem like,” and Sherlock had said, “Of _course_ , but you never,” and John had said, “well, if you’d ever asked,” and Sherlock had said, “how _could_  I have,” and John had said, “Bloody _time travel_.”

“You know,” John said, sometime later, when his hands were tangled in Sherlock’s hair and his lips were feeling bruised, “the _funny_  thing is that we really have _Mycroft_  to thank for this.”

“All right,” Sherlock said, extracting himself, “that’s it, you’ve ruined it entirely.”


	2. Coda

**Notes for the Chapter:**

> Accidentally wrote a coda to this. Whoops!

“Did you find the book?” John said, not looking up from his book as Sherlock re-materialized in the sitting room.

“Yes,” Sherlock said.  “Also I think I may have seduced you, a bit.”

“Mm,” John said.  “The time on the kitchen table?”

“No, I did that a year ago or so,” Sherlock said.  

“Ah - the one where you woke me up in the middle of the night, then?” 

“Haven’t done that one yet, though let’s assume I apologize in advance,” Sherlock said.

“Apology accepted retroactively,” John said.  “I’m trying to think - was it the time you showed up in your pajamas?”

“How many different me’s are you sleeping with?” Sherlock said, flopping down on the sofa.

“I’ve absolutely no idea,” John said.  “I don’t usually bother to ask once you start taking off your clothes.  Got me in trouble once, if you’ll recall.”

“I do,” Sherlock said.  “Fondly.  And relevantly, because I just suggested to a very young you that you ask about that very occasion.”

“So you _were_  trying to seduce me!”

“Of course I was,” Sherlock said.

“It was for the best,” John said.

“I think so,” Sherlock said.

There was a silence while Sherlock thought about the second first time John had kissed him.  It had been lovely; a perfect mix of desperation and sweetness, all freshness and terror and yearning, an absolutely - 

“Mm, remember the time we did it in a cupboard at the Yard?” John said.

“A _cupboard_  at the _Yard_?” Sherlock said.  “When did _that_  happen?”

“I don’t know,” John said, waving a hand.  “Seven or eight years ago?  I guess you were even older than you are now.  I actually wondered if you’d got bored of me in your present.”

“That’s impossible,” Sherlock said promptly.  “I’ll never be bored of you.”

“If you say so,” John said, a smile playing at his lips.

“Though I am glad I have public sex at the Yard to look forward to,” Sherlock said, pleased.  “Hang on, is that what started your exhibitionist streak?”

“No comment,” John said.


End file.
